First you have to distribute the 5 to the 4, and 2x. So you get 20, and 10x. then distribute the negative to the 8x then the 12. Now you get -8x and 12. so put that all together you get:
20+10x-8x+12=68
Now combine like terms. So:
2x+32=68
subtract over the 32:
2x=36
divide by 2
x=18
And thats your final answer!